Computer systems typically comprise a combination of computer programs and hardware, such as semiconductors, transistors, chips, circuit boards, storage devices, and processors. The computer programs are stored in the storage devices and are executed by the processors. Computers are often connected in networks, such as the Internet, and a user at one computer, often called a client, may wish to access information at multiple other computers, often called servers, via a network. Although this connectivity can be of great benefit to authorized users, it also provides an opportunity for unauthorized persons (often called intruders, attackers, or hackers) to access, break into, or misuse computers through the use of malicious programs. This connectivity also provides an increased chance that a computer will receive data or programs that contain inadvertent errors.